My car was running without oil pressure for a short time, how do I know if any damage was done?

Question:

While driving my 1968 Pontiac on the freeway, I noticed the oil pressure warning light was on. I don’t know how long it was lit, but it was at least a few minutes. I drove the car another 12 minutes to reach my house and immediately shut off the engine. The engine was quiet and seemed to run as good as usual, but I am concerned that I may have damaged something by running without oil pressure. How can I know if any damage was done?

Answer:

It is almost certain that failure of the oil pressure switch, and not an actual loss of oil pressure, caused the light to remain on. If you drove at freeway speeds for more than 15 minutes without oil pressure, your engine would have failed. The easiest way to determine whether the engine’s oil pressure is adequate is to install an oil pressure gauge in the hole where the warning light switch is installed (usually adjacent to the oil filter). Start the engine and observe the gauge. Normal oil pressure for a ’68 Pontiac will vary according to the engine, weight of the oil and engine temperature, but a good rule of thumb is that a healthy engine at operating temperature will produce a minimum of about 25 psi at idle and a maximum of about 60 psi at high speed. If you are not overly concerned with originality, you can permanently mount the gauge in your car. But if you want to keep the system original, simply replace the oil pressure warning switch with a new one available from any auto parts store or Pontiac dealer.